Process of desulphidizing and desulphurizing sulphur minerals



Jan.`31, 1928. v 1,657,711

M. F.'cooLBAuGl-| ET AL PROCESS- oF DESULPHIDI'ZING Ama .DESULPHURIZING suLPHUR MINERAL-s Filed Aug. 4, 1922 Ulululu 1 lululululu' llll Il f/ i Patented Jan. Y31, 1928.

MELVILLE FULLER COOLBAUGH AND JOHN BURNS SIGNORS T THE COMPLEX GRES RECOVERIES A CORPORATION 0F COLORADO. f

READ, OF GOLDEN, COLORADO, AS- COMPANY', OF DENVER, COLORADO,

PROCESS OIE 'DESULPHIDIZING AND DESULPHURIZING SULIE'HLUR MINERALS.

, Application filed August 4, 1922. serial No. 579,714.

The object of Athis invention is to provide a more rapid and'efticient method for the elimination of sulphur fromsulphur bearing minerals. lThis is accomplished by roasting sulphide minerals under conditions which will form appreciable quantities of sulphates, and other highly oxidized com- I pounds, which in turn carry oxygen into the bed and rapidly oxidize the remainder of the sulphide.

' The usual practice heretofore for the elimination of sulphur from a sulphide mineral has beeny to roast the mineral with an excess of air forming oxides of the metals directly and liberating sulphur dioxide gas.

. In this operation `the sulphide mineral and air for oxidation vare caused to travel coun ter-currently in which case only a small quantity of sulphates form, and these form only after the greater part of the sulphide sulphur hasbeen/eliminated. In order to decompose the sulphates it has been necessary to heat to a high temperature with or without the addition of carbonaceous matter.

Our inventioncauses the desulphidizing of sulphide "minerals to be effected by the formation of sulphates in the presence of sulphides, yandl these two compounds when brought to the right temperature conditions interact to formfmetal oxides and sulphur dioxide. l

This process is carried on as follows: The mineral to be desulphidized is fed into the top of a roasting furnace, which may be of the type indicated in the accompanying drawing, wherein the process as a whole is diagrammatically illustrated. By preference this furnace is one of the mechanically operated superimposed 4hearth types, al though other types may be used if desired. The air for oxidation is added with the mineral and both travel together continuously in the same direction, that is, con-l currently, throughout the desulphidizing zone. The temperatures on the first hearths will be low, ranging from S50-500 degrees C. but will rise on the succeeding hearths as the desulphidizing progresses until a maximum of about 900? C. is attained. During this progress through the furnace sulphates will form in the upper cooler zone in the presence of sulphides which are being reacted upon to form metal'oxides and sulphur dioxide by the action of the air. As the sulphates and sulphides travel together into the hotter zone an interaction takes place between them, whereby oxides andA sulphur dioxide are formed. If the proportion of sulphates to sulphides could be closely regulated in the above operation, the calcine could be completely roasted to an oxide and discharged from the furnace, when this reaction is completed. Usually, however, the sulphate will predominate at the completion of the desulphidizing reaction, so that further means must be employed to decompose such sulphates if a completely desulphurized product is desired. The decomposition of the sulphate is readily 'effected by passing the ore from the desulphidizing zone into a lower part of the furnace separated by a seal which Ymay be formed by ore or other means. In the lower part of the furnace the temperature may be maintained by mufiies and the gases taken away from each hearth as rapidly as possible, which is the condition most favorable for decomposing sulphates. If desired, regulated quantities of sulphides may be added to decompose the excess of sulphates by the same chemical reaction as is involved in the desulphidizing zone. The gas from the desulphatizing zone which will be highly concentrated in sulphur dioxide and sulphur trioxide may be returned to the top of the furnace to be mixed with ore and thus aid in the formation of sulphates which are highly desirable for this zone.

From the above description it is plain that the desulphidizing of asulphide mineral is accomplished by causing sulphates to form in the presence of sulphides, `and then causingithe sulphates which are strongly oxidizing to react with the sulphides which are strongly reducing 'and form oxides and su1` phur dioxide. The formation of the sulphates is accomplished by maintaining a high concentration of sulphur gases at regulated temperatures for an appreciable time in contact withthe material to be sulphatized. This is effected by moving the minerals and gases rich in oxids of sulphur in 'the same direction in the desulphidizing other metals such as copper and lead have similar reactions. Zinc sulphide, lwith any accompanying iron sulphide, charged into the furnace together Withair for oxidation, will ormat 350 @-500o C. ferrie oxide and sulphur dioxide as follows:

QFeSg -l- 110 =Fe2O3 +4502 The ferrie oxide thus formed has a marked catalyticA action upon SO2 and oxygen to form S03. Some ferrie and ferrous sulphates may be formed simultaneously with the ferrie/oxide. Zinc sulphide does not oxidize as readily as iron sulphide, but someA zinc oxide will form during oxidation of the iron Zinc oxide willlreact with sulphur trioxide to form zinc sulphate.

At higher temperatures, above 525"V C. zinc sulphate reacts with the remaining zinc sulphide as'follows:

Any zinc sulphate in excess of the above equation is decomposed under the influence of heat by removing the sulphur gases as rapidly as possible and by introducing a regulated quantity of sulphide mineral to reduce such excess of sulphate.

This process reveals a means whereby a sulphide mineral can be desulphidized very urapidly, producing an oxide as the final product. The rapidity of the reaction will assurevgreater tonnage per furnace than 1s now roasted, which in turn will give a higher temperature which is favorable for the completion of the roast.

The process is especially adopted to the roasting of zinc sulphide concentrates preliminary to the production of metal zine in the retort, and also the production of zinc oxide on the Wetherill grate. The requirements for these two operations are that the calcine should contain a minimum quantity of sulphur and that the roasting should be performed at a minimum expense. By employing the principle of oxidation by means of a sulphate both requirements are met.

le claim:

l. A process of desulphurizing metalliferous sulphide material in a multi-stage roasting operation which comprises irst subjecting the material to a, sulphatizing roast in an atmosphere containing an excess of sulphur trioxid while carrying the material to a temperature at which snlphates would decompose if in an atmosphere devoid of sulphur trioxid, conducting gases containing sulphur trioxid and free oxygen in concur rent contact with the sulphide material under treatment during such step; withdraw ing the sulphatized material from contact with sulphatizing conditions and heating the same while rapidly withdrawing the gases containing sulphur trioxid from contact with the heated material, to allow desulphatizing to be conducted rapidly; and

` introducing the gases evolved in the last mentioned step with air into the sulphatizing zone.

2. A process of desulphidizing sulphide material which comprises the step of subjccting the material to a sulphatizing roast in an atmosphere containing an excess of sulphur trioxid while carrying the material to a temperature at which sulphates would decompose if 4in an atmosphere devoid of sulphur trioxid, conducting gases, produced extraneously to such step, which gases contain sulphur trioxid and free oxygen, in concurrent contact with the sulphide material under treatment during such step, to form metallic oxides and sulphur gases by reaction of the sulphides and produced sulphates.

3. A process for desulphidizing sulphide minerals comprising roasting the same with metallic sulphates and moving the minerals and gases containing SO3 in excess concurrently during the roast and thereafter tur ther roasting the said materials, with the S03 kept as low as possible to permit ot" the formation of oxide.

4. A process of desulphnrizing metallil'- crous sulphide material in a multi-stage roasting operation which comprises first subjecting snlphie material containing iron and other metal sulphides to a sulphatizfiing roast in an atmosphere containing' :in excess of sulphur trioxid while carrying the material to a temperature at which snlphates would decompose if in an atmosphei e devoid of sulphur trioxid, the iron oxid formed Aserving as a catalyst for oxidation of SO: to SOM conducting gases containingY sulphur trioxid and free oxygen in concurrent contact with the sulphide material under treatment during such step; withdrawing the snlphatizcd material from contact with snlphatixin'g con- .ditions and heating the same while rapidly1 withdrawing the gases containing sulphur lofi l substantial decomposition of the sulphatesy ymation of oxides.

trioxid from contact with the heated material, to allow desulphatizing to be conductedv rapidly; and introducing the gases evolved in such step with air into the sulphatizingv zone. i

5. A desulphidizing process for minerals comprising roasting togetherv metallic sulphides and sulphates for the formation of oxides and sulphur gases and advancing the minerals concurrently with gases containing an excess of SOS over'that generated by the roasting reaction.

6. A process of desulphurizing metal sulphide material which comprises causing the y material to travel. downwardly through a furnace while subjecting the same to extraneous heating, passing gases containing sulphur trioxid and free oxygen, in concurrent contact with the ore during the iirst stage of they said furnace treatment, continuing Y the heatingof the sulphatized material while passing through the later stage of the process, while rapidly withdrawing the' evolved gases containing sulphur trioxidfrom said later stage of the process, causing the sulphatized material to form a gas seal between the first stageand the later stage ofthe treatment,"withdiawing the gases from said first stage at above said seal, and conducting thee gases evolved in the second stage into the first stage for utilization as a sulphatizing agent therein.'

y7. A process for desulphidizing sulphide minerals comprising roasting the same with air and under conditions favorable to the efiicient formation of metallic'sulphates, and advancing the materials and gases concurrently during the roast and thereafter heating the sulphatized material while rapidly leading away the sulphur trioxid formed.

8. A process for desulphidizing sulphide minerals containing iron comprising roasting the same for the formation of metallic oxides and sulphur oxides under conditions favorable toI the efficient formation of metallic sulphates, and advancing the minerals and gases concurrently, and thereafter heating the sulphatized material while rapidly leading away the sulphur trioxid formed.

' 9. A process for -desulphidizing sulphide minerals containing iron comprising roast- Tiiig the same for the formation of metallic oxides and sulphur oxides under conditions favorable to the eiicient formation of metallic sulphates, maintainin SO3 concentration in the gases high enougi to insure against desired, and advancing the materials and gases concurrently and thereafter further roasting the said materials, withv the S03 kept as low as possible to permit of the for- 10. A process of desulphurizing metal sulphide material which comprises causing the material to travel through a furnace while continuing the heating `of the sulphatized material while passing through the later stage of the process, while rapidly withdrawing the evolved gases containing sul-- phur trioxid from said later stage yof the process, maintaining a gas seal between the first stage and the later stage of the treatment, withdrawing the gases from said first stage in advance of said seal, and conducting the gases evolved in the second stage into the first stage for utilization as a sulphatizing agent therein. n

n ll. A process for desulphidizing sulphide minerals comprising roasting the same for formation of metallic oxides and sulphur oxides under conditions favorable to the efficient formation of metallic sulphates and reactionof said sulphates with sulphide pai'- ticles to oxidIz-:e the latter, maintaining SO3 concentration in the gases high enough to insure against decomposition of the sulphates during` said reaction, and theiilowering said S concentration for the ready decomposition of the sulphates and formation of oxides therefrom.

l2. A process for desulphidizing sulphide minerals comprising .roasting the same for formation of metallic oxides and sulphur' oxides under conditions favorable to the efficient formation of metallic sulphates and reaction of said sulphates with sulphide particles to oxidize the latter, maintaining SOS concentration in the gases high enough to insure against decomposition of the sul'- phates during said reaction, and separating the mineralsl from said gases for decomposition of the sulphates in an atmosphere of low SO3 content, and maintaining said S03 content low in the atmosphere surrounding such materials during desulphatiziiig.

13. A process for desulphurizing sulphide minerals comprising roasting the same for the formation of oxides of the metals present and of sulphur, advancing the minerals and liberated gases together under conditions favorable to the efficient formation of 'metallic sulphates whereby the sulphates reerals containing iron comprisin roasting the same with air for the formation of metallic oxides including ferrie oxide and sulphur oxides, whereby the ferrie oxide acts catalytically to form S03 from the liberated S02 and oxygen of the air, whereby the S03 reacts with certain oxides to form metallic sulphates thereof, and whereby the sulphates yreact with sulphides to form metallic oxides and sulphur dioxide which metallic oxides and dioxide are again converted into sulphates and trioxide, and introducing S03 gas sufficient to maintain a concentration thereof to prevent decomposition of the sulphates.

15. A process for desulphurizing sulphide minerals containing iron comprising roasting the same with air for the formation of metallic oxides including ferrie oxide and sulphur oxides, whereby the ferrie oxide acts catalytieally to form S03 from the liberated 'S0g and oxygen of the'air, whereby t-he SQ3 reacts with certain oxides to form metallic sulphates thereof, and whereby the sulphates react with sulphides to form metallic oxides and sulphur dioxide which metallic oxides and dioxide are again converted into sulphates and trioxide, introducing S03 gas sulicient to maintain a concentration tuereof to prevent decomposition of the sulphates, removing the sulphates from said gases and heating the sulphates in an atmosphere low in S03 to decompose the sulphates, form oxides and liberate S03, and. introducing said S03 to the sulphide minerals being roasted and resulting oxides to accelerate the oxidation of the sulphides by formation of sulphates. p

`16. A process for desulphurizing sulphide minerals comprising roasting the same with air for the formation of metallic oxides and sulphur oxides under conditions favorable tothe elicient formation of sulphates, whereby the sulphates vreact with sulphides to form metallic oxides and sulphur dioxide into sulphates by S03 present, introducing S03 gas suflicient to maintain a concentration thereof to prevent decomposition of the sulphates,.removing the sulphates from said gases and heating the sulphates in an atmospherelow in S03 to decorn ose the sulphates, form oxides and liberate 03, and introducing -said S03 t0 the sulphide minerals being roasted and the resultinfr oxides to gas sufficient tol maintain a concentration.

thereof to prevent decomposition of the sulphates.

18. A process of desulphurizing metal sulphide material which comprises causing sulphide material containing iron and other sulphides to .travel through a furnace while subjecting the same to extraneous heating, passing gases containing sulphur trioxid and free oxygen,fin concurrent contact with the ore during the firstv stage of the said furnace treatment, continuing the heating of the sulpha-tized material while passing through the later stage of the process, while rapidly withdrawing the evolved gases containing sulphur trioxid from said later stage of the process, withdrawing the ases from said first stage at near the end t iereof, and conducting the gases evolved in the second stage into .the first stage for utilization as a sulphatizing agent therein.

In testimony whereof we ailix our signatures.

MELVILLE FULLER- eooLBAUGH.'

which metallic oxides are again converted JOHN BURNS READ. y 

